The present invention concerns a thermoreversible food product.
The term xe2x80x9cthermoreversiblexe2x80x9d is intended to mean that which is convertible from a gel phase at room temperature to a liquid phase at a temperature elevated above room temperature. The term xe2x80x9cthermoreversiblexe2x80x9d also includes the preferred term xe2x80x9cthermointerchangeablexe2x80x9d as that which is convertible from a gel phase at room temperature to a liquid phase at a temperature elevated above room temperature and is reconvertible back to a gel phase when cooled to room temperature.
It is an object of the present invention to provide a food product which is gelled at room temperature and which, following heating in a microwave, has completely melted.
It is a further object of the present invention to provide a bilayered food product in which both layers are gelled at room temperature and in which, following heating in a microwave, both layers are completely melted, but remain as substantially separate liquid layers.
It is a still further object of the present invention to provide a bilayered food product in which colour migration between the two layers is substantially eliminated, after the food product has been microwaved.
It is also an object of the present invention to provide a multilayered food product, in which all layers are gelled at room temperature and in which, following heating in a microwave, at least two of the layers are completely melted, but remain substantially separate liquid layers, and in which colour migration, between those layers, is substantially eliminated.
The food product may be, for example, a coffee liqueur product, having a base layer containing coffee and alcohol and having a top layer containing an animal fat or a mixture thereof, a vegetable fat or a mixture thereof or a mixture of animal and vegetable fats. It is envisaged that both layers of such a food product may be melted to their respective liquid phases and heated by means of a microwave.
In a first embodiment, the invention provides a food product having a top layer comprising less than 70%, preferably less than 65%, more preferably less than 60%, most preferably less than 50%, (w/w) water and an amount of at least one top thermoreversible setting agent sufficient to maintain the top layer in a gel phase at room temperature whilst permitting thermoreversion to a liquid phase at a temperature elevated above room temperature, with the proviso that sodium caseinate is substantially absent.
Preferably, the top layer contains 40-65% (w/w) water, more preferably 40-50% (w/w) water.
More preferably, the top layer contains at least 40% (w/w) water.
By xe2x80x9croom temperaturexe2x80x9d, we mean at or below 23xc2x0 C. By xe2x80x9ctemperature elevated above room temperaturexe2x80x9d, we mean that the temperature in the relevant layer is, following heating by microwave, at or above 40xc2x0 C., preferably at or above 45xc2x0 C., more preferably at or above 50xc2x0 C., most preferably at or above 55xc2x0 C.
Preferably, the food product additionally includes a base layer comprising at least one base thermoreversible setting agent in an amount sufficient to maintain the base layer in a gel phase at room temperature, whilst permitting thermoreversion to a liquid phase at a temperature elevated above room temperature.
Advantageously, the top layer additionally comprises at least one top emulsifier and more than 15% (w/w) fat. More advantageously, the top layer contains more than 20% (w/w) fat and most advantageously 20-40% (w/w) fat. The fat can be of animal or vegetable origin, or a mixture thereof.
Preferably, the at least one top thermoreversible setting agent is combined with the at least one top emulsifier selected from at least one mono-glyceride of a fatty acid or mixtures thereof; at least one di-glyceride of a fatty acid or mixtures thereof; at least one sucrose ester or mixtures thereof; or mixtures of two or more of mono-glycerides, di-glycerides and sucrose esters. More preferably, the top layer contains 0.1 to 1.75% (w/w) of the at least one top thermoreversible setting agent. Even more preferably, the base layer contains 0.1 to 3.5% (w/w) of the at least one base thermoreversible setting agent.
In a conventional cream liqueur system, sodium caseinate is used as an emulsifier and as a stabiliser. However, in a microwavable food product, which is the subject of the present invention, the co-presence of sodium caseinate and alcohol causes skin formation when the food product is microwaved. It was, therefore, necessary to preclude the use of sodium caseinate.
It is believed that the present invention overcomes the problem of colour migration by providing a top layer having less than 70% (w/w) waterxe2x80x94this reduces hydrogen ion migration, which is accompanied by colour migration, from the base layer to the top layer, which hydrogen ion migration affects the pH of the top layer and may also be accompanied by a breakdown in the stability of the top layer""s emulsion, causing it to lose its thermoreversibility.
Suitable emulsifiers should not form a skin on the upper surface of the top layer when the top layer is heatedxe2x80x94it is thought that such skin formation is related to denaturation of a proteinaceous emulsifier, so that such emulsifiers should be avoided. Suitable emulsifiers must be comestible and include, but are not limited to, mono-glycerides of fatty acids, di-glycerides of fatty acids, sucrose esters or mixtures thereof. Sucrose esters endow good stability, but their organoleptic properties need to be improved.
Suitable top and base thermoreversible setting agents must be comestible and include, but are not limited to, gelatine, agar, gellan gum, methyl celluloses, guar gum, carrageenan (preferably kappa and/or iota carrageenan), gum arabic, xanthan gum, locust bean gum or mixtures thereof. When the thermoreversible setting agent is gelatine, the top layer may contain 0.75 to 1.75% (w/w), more preferably 1.0 to 1.5% (w/w) gelatine and the base layer may contain 1.5 to 3.5% (w/w), preferably 2.0 to 3.25% (w/w), more preferably 2.25 to 2.75% (w/w) gelatine. When the thermoreversible setting agent is carrageenan, the top layer may contain 0.1 to 1.0% (w/w), preferably 0.25 to 0.75% (w/w) carrageenan and the base layer may contain 0.1 to 1.5% (w/w), preferably 0.2 to 0.75% (w/w) carrageenan. If a mixture of carrageenans is used, they may be present in a ratio of 2:1 to 1:2, preferably 1.5:1 to 1:1.5 (ratio of kappa to iota carrageenan).
Gelatine is obtained from collagen found in animal tissues, including the skin, tendons and ossein of bones.
In a second embodiment, the invention provides a cream liqueur food product having a top layer comprising (i) less than 70% (w/w) water; (ii) more than 15% (w/w) fat; (iii) at least one top emulsifier; and (iv) at least one top thermoreversible setting agent, the at least one top emulsifier and the at least one thermoreversible setting agent being sufficient to maintain the top layer in a gel phase at room temperature, whilst permitting thermoreversion to a liquid phase at a temperature elevated above room temperature, with the proviso that the, or each, top emulsifier or setting agent is not sodium caseinate.
The invention also provides a method for forming a layer of a food product, comprising at least one thermoreversible setting agent and/or at least one emulsifier, the method comprising the steps of providing a first liquid phase at a temperature below room temperature; providing a second liquid phase comprising an amount of at least one setting agent and/or at least one emulsifier sufficient to maintain a mixture of the first and second liquid phases, when mixed in a thermoreversible gel phase at room temperature with the proviso that the, or each, setting agent and/or emulsifier is not sodium caseinate, the second liquid phase being at a temperature raised above room temperature; and mixing the first and second liquid phases to obtain the top layer.
By xe2x80x9craised temperaturexe2x80x9d is meant a temperature at or above 30xc2x0 C., preferably at or above 35xc2x0 C.
It will be appreciated that, if the food product comprises a top layer and a base layer, the aforementioned method comprises the steps of providing first and second base phases; mixing the first and second base phases and allowing the thus mixed first and second base phases to set; providing first and second top phases; mixing the first and second top phases and allowing the thus mixed first and second top phases to set on the base layer.
According to a further embodiment of the invention there is provided a method for forming a layer of a food product comprising at least one thermoreversible setting agent and/or at least one emulsifier sufficient to maintain the layer in a gel phase with the proviso that the, or each, setting agent and/or emulsifier is not sodium caseinate.
It will be appreciated that, if the food product comprises a top layer and a base layer, the aforementioned method comprises the steps of providing the first layer, allowing the first layer to set; providing the second layer and allowing the second layer to set on the base layer.
Advantageously, the food product is a cream liqueur. By xe2x80x9ccream liqueurxe2x80x9d is meant a bi- or multi-layered beverage whose top layer contains fat of animal and/or vegetable origin and at least one of whose other layers contains alcohol. If the cream liqueur is bilayered, the volume ratios of the top and base layer should be in the range 1:1 to 1:12, preferably 1:1 to 1:10, most preferably about 1:2. Hereinafter is exemplified a cream liqueur food product in the form of an xe2x80x9cIrish Coffeexe2x80x9d having two layers, namely a base layer and the top layer. It will, of course, be appreciated that the cream liqueur food product may, alternatively, be a xe2x80x9cFrench Coffeexe2x80x9d if brandy is added instead of Irish whiskey in the base layer. Similarly, a xe2x80x9cRussian Coffeexe2x80x9d (vodka) or xe2x80x9cCaribbean Coffeexe2x80x9d (rum), etc., are also envisaged. The present invention is not of course limited to coffee-containing cream liqueur food products (coffee cream liqueur food products)
Any comestibly suitable alcohol in the base and/or top layer may be selected from spirits, such as neutral spirit, whiskey, whisky, brandy, vodka, rum or a mixture thereof. Preferably, the base layer contains 7 to 20% (w/w), preferably 8 to 12.5% (w/w), more preferably 8.75 to 10% (w/w) alcohol. More preferably, the top layer contains 7 to 20% (w/w), preferably 8 to 12.5% (w/w), more preferably 8.75 to 10% (w/w) alcohol. Advantageously, the cream liqueur food product contains 7 to 20% (w/w), most preferably 8.75 to 10.5% (w/w) alcohol.
The invention will now be described and exemplified in the following examples, which are not intended to limit the scope of the invention.